1. Technical Field
The present disclosure generally relates to integrated circuit design, and in particular to level shifter circuits.
2. Description of Related Art
Modern integrated circuits, such as microprocessors or System-on-a-Chip (SoC) designs, are increasingly required to operate on low power levels such as, for example, in consumer electronic devices where conservation of battery power is very important. Although processor cores may be designed to operate at low power levels, the Input/Output (I/O) interfaces and memory modules may require higher power levels. In some cases, individual cores included in multi-core processors may operate at different supply voltage levels. Such “individualized” operational voltages give rise to multiple voltage “domains” or “islands” on a chip. In other words, modern multi-core architectures and SoC designs include multiple voltage domains on the chip—each voltage domain supplying a different voltage to the corresponding circuitry.
Because of different operating voltages, two circuits on a semiconductor chip or die may not be able to interface (or “talk”) with each other unless a mechanism is employed to facilitate a smooth transition of signals from one circuit at one voltage level to the signals usable in the other circuit at another voltage level. A level shifter circuit is one such mechanism that connects one digital circuit operating at one voltage level to another digital circuit that works on another voltage level. Thus, when a signal must be transferred from one voltage domain to another voltage domain, a level shifter may be employed at the interface between these two voltage domains to convert the signal's voltage level. For example, an “up-conversion” level shifter may be needed when a signal passes from low voltage domain to a high voltage domain. On the other hand, a “down-conversion” level shifter may convert a signal from a high voltage domain (i.e., having a high voltage value) to a respective signal to be sent to a low voltage domain (i.e., having a low voltage value).